Field of the Invention
The present invention relates to an automatic transmission for a vehicle. More particularly, to a planetary gear train of an automatic transmission for a vehicle that improves power delivery performance and fuel economy by achieving eleven forward speed stages with a minimum number of constituent elements being used and improves silent driving of the vehicle by using an operation point positioned at a low engine speed.
Description of Related Art
Recent increases in oil price are triggering stiff competition in enhancing fuel consumption of a vehicle.
In this sense, research for an engine has been made to achieve weight reduction and to enhance fuel consumption by so-called downsizing and research for an automatic transmission has been made to simultaneously provide better drivability and fuel consumption by achieving more shift-stages.
However, in the automatic transmission, as the number of speed stages increase, the number of internal components (particularly, planetary gear sets) increase, and as a result, a length of the transmission increases. This may deteriorate installability and/or power flow efficiency and may increase production cost, and weight.
Therefore, in order to maximally enhance fuel consumption of an automatic transmission having more shift-stages, it is important that better efficiency is derived by less number of parts.
In this aspect, in recent years, 8-speed automatic transmissions tend to be implemented and the research and development of a planetary gear train capable of implementing more speed stages has also been actively conducted.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.